The following description of the background of the invention is provided to aid in understanding the invention, but is not admitted to be or describe prior art to the invention.
Protein kinases and protein phosphatases regulate a wide variety of cellular processes including metabolism, cell proliferation, cell differentiation, and cell survival by participating in signal transduction pathways. Alterations in the cellular function of a protein kinase or protein phosphatase can give rise to various diseased states in an organism. For example, many types of cancer tumors are associated with increases in the activity of specific protein kinases. Cell and tissue degeneration can also be associated with decreases in the activity of particular protein kinases.
Cellular signal transduction is a fundamental mechanism whereby extracellular stimuli are relayed to the interior of cells. One of the key biochemical mechanisms of signal transduction involves the reversible phosphorylation of proteins. Phosphorylation of amino acids regulates the activity of mature proteins by altering their structure and function.
Phosphate most often resides on the hydroxyl moiety of serine, threonine, or tyrosine amino acids in proteins. Enzymes that mediate phosphorylation of cellular effectors fall into two classes. While protein phosphatases hydrolyze phosphate moieties from phosphoryl protein substrates, protein kinases transfer a phosphate moiety from adenosine triphosphate to protein substrates. The converse functions of protein kinases and protein phosphatases balance and regulate the flow of signals in signal transduction processes.
Protein kinases are divided into two groups--receptor and non-receptor type proteins. Receptor protein kinases comprise an extracellular region, a transmembrane region, and an intracellular region. Part of the intracellular region of receptor protein kinases harbors a catalytic domain. While non-receptor protein kinases do not harbor extracellular or transmembrane regions, they do comprise a region similar to the intracellular regions of their receptor counterparts.
Protein kinases are divided further into three classes based upon the amino acids they act upon. Some incorporate phosphate on serine or threonine only, some incorporate phosphate on tyrosine only, and some incorporate phosphate on serine, threonine, and tyrosine.
In an effort to discover novel treatments for diseases, biomedical researchers and chemists have designed, synthesized, and tested molecules that inhibit the function of protein kinases. Some small organic molecules form a class of compounds that modulate the function of protein kinases.
The compounds that can traverse cell membranes and are resistant to acid hydrolysis are potentially advantageous therapeutics as they can become highly bioavailable after being administered orally to patients. However, many of these protein kinase inhibitors only weakly inhibit the function of protein kinases. In addition, many inhibit a variety of protein kinases and will therefore cause multiple side-effects as therapeutics for diseases.
Some indolinone compounds, however, form classes of acid resistant and membrane permeable organic molecules that potently inhibit only specific protein kinases. Indolinone synthesis, methods of testing the biological activity of indolinones, and inhibition patterns of some indolinone derivatives are described in International Patent Publication No. WO96/40116, published Dec. 19, 1996 entitled "Benzylidene-Z-Indolinone Compounds for the Treatment of Disease" by Tang et al. (Lyon & Lyon Docket No. 223/298) and International Patent Publication No. WO 96/22976, published Aug. 1, 1996 by Ballinari et al., both of which are incorporated herein by reference in their entirety, including any drawings.
Despite the significant progress that has been made in developing indolinone based pharmaceuticals, there remains a need in the art to identify the particular structures and substitution patterns that cause inhibition of particular protein kinases and other specified biological activities.